I'd opt for option 1, assuming that the earned EQM/EQP are useful to you for the US-LHR portion. We did this recently for SJC...LHR, LGR...SJC with the parts to Italy (LHR-FCO, VCE-LGW) down with a BA business award. Maximizes earned EQM and saves money over buying a BA business fare (not one of your listed options...and for good reason

).
Cheers.